Sahih Muslim Book 007, Hadith Number 2844.
Chapter : Ifrad and Qiran (combining Hajj and Umra in one Ihram) in the performance of pilgrimage.
Anas (Allah be pleased with him) said: I heard Allah's Apostle (way peace be upon him) pronouncing Talbiya for both Hajj and Umra. Bakr (one of the narrators) said: I narrated it to Ibn 'Umar, whereupon he said: He (the Holy Prophet) pronounced the Talbiya for Hajj alone. I met Anas and narrated to him the words of Ibn 'Umar, whereupon he said: You treat us not but only as children. I heard Allah's Messenger (may peace be upon him) pronouncing Talbiya both for 'Umra and Hajj.